CINCINNATI (AP) — The mayor of Cincinnati has tearfully apologized to city police after his office unwittingly approved a proclamation honoring a man suspected of killing an officer in an ambush.

Mayor John Cranley delivered his apology Thursday at the police union hall, saying the proclamation was stamped by a new staffer. He said he also called the officer's widow to apologize.

"This was a huge mistake," said Cranley. "It's not done intentionally. It's human error, but the buck stops with me."

The proclamation designated June 1, 2017, as "Tre Day" in honor of Trepierre Hummons. Investigators say Hummons was hoping for "suicide by cop" when he killed Officer Sonny Kim in June 2015 before being gunned down by another officer.

The mayor's office received the request for the proclamation from Ronald Hummons for his son Tre's birthday. It did not provide the son's full name, Cranley said. It said a proclamation would recognize work done by a foundation, set up following his son's death, to address mental illness.

Cranley's office receives proclamation requests from Cincinnati residents every week. Many are vetted by his press office and the mayor doesn't see them all.

Ronald Hummons also reached out to a local politician and a city council member, who said he didn't know about the request.